[BC] Humming Preamps

[Gary Peterson]

> I'm still having issues with humming in all our mic, stereo, and  phono
> preamps. It's a buzzing sound that seems faster higher  frequency than 60
> cycle hum. More like RF static. It happens in all 4  of our studio booths
> on two floors. It's so bad we can't use our  turntables. I got an
> electrician to come out and he ran new ground  wires for the building
> service and switch panel and replaced old  vibrating breakers. It still
> hums. He suggests running 20 amp lines  with isolated ground to plug
> strips for each booth. Before I lay down  another $800 does this sound
> like it might fix our problem? Also do  the high end $450 Furman or
> Monster power conditioners work any  better than the $150 Furman PL-8 rack
> mount conditioners we have? I'm  starting to fear thousands spent in a
> wild goose chase. By the way a  Verizon tech had to install inline RF
> filters to cut the humming and  noise from our phone hybrids. I've never
> met a building this noisy.
> Thanks in advance.
> Shelby

I've seen two situations where hum or buzz got into radio station audio
equipment via the power line.  The first time, it was a water heater that
was defective.  Every time the heating element came on, hum appeared in
several pieces of audio gear.  Some were tube and some were solid-state.
This was circa 1968.  It was located by flipping breakers in each panel in
the building until the hum quit.  A replacement water heater solved that
problem.  I guessed that there was leakage between the 240 VAC in the
heating element to the plumbing and electrical ground.

At another site, circa 1985, a buzz appeared, from time to time, in the
preamps on the Carousels in the automation system.  This was traced to some
recently installed track lighting, with a SCR dimmer, in another office in
the building.  All attempts at filtering out the noise, at the source,
failed.  We finally bought them a Variac-type of dimmer.

If you can do it, start shutting down various circuits and see what happens.
A couple of FRS handheld radios would come in handy.

Gary, K?CX